In co-pending application, Ser. No. 899,655 of some of the inventors herein, a new family of polymerization initiating systems is disclosed based on complexes formed from organic ethers, in conjunction with Lewis acids. Polymerizations conducted with such systems have been found to result in cationic polymerizations, sometimes termed "living" polymerizations, which polymerizations are terminalationless, and operate without chain transfer. Even though such polymerizations have produced polymers with fairly broad molecular weight distributions, the systems can be used to produce polymers of considerable commercial importance.
It has now been found possible, however, to conduct such polymerizations in a way in which the M.sub.w /M.sub.n values of the polymers produced are relatively small, i.e., the molecular weight distribution of the resulting polymer molecules is particularly narrow. As is generally recognized, it is frequently desirable to prepare polymers having narrow molecular weight distributions for a variety of reasons, and polymers exhibiting such characteristics, for example, have been used as motor oil additives, as well as in paint formulations, to desirably improve the viscosity indices in such oils and paint. In addition, such polymers can be employed as calibration standards in connection with gel permeation chromatography, and in various other applications.
In the past, techniques such as, for instance, fractionation of polymeric materials exhibiting a broad spectrum of molecular weights have been resorted to in preparing polymers having a narrow molecular weight distribution. Inevitably, however, such methods are both laborious and expensive, and thus are undesirable at least for those reasons.